This invention relates to a thermal recording print head which is used in various heat-sensitive recording systems as a printer, a facsimile or the like.
A conventional thermal recording print head is constructed as shown in FIG. 1. A process of driving such a print head is shown in FIG. 2. In FIG. 2, the horizontal axis represents time. In the operation of the FIG. 2 process, one printing line is divided into four blocks shown on the vertical axis. "Transferring and printing" appearing in FIG. 2 as "T" and "P" means that a time series signal from an external signal source is stored in a shift register or the like during the transfer, and upon completion of the storage, printing is carried out simultaneously. The external signal is transferred to the second block after the printing in the first block is completed. Printing is therefore carried out successively in such a fashion. For instance, in the case where a large part of a line is blank, printing can be carried out with one line as one block, and in this case, one line printing time is much shorter. However, since sheet feeding time is always included for a line to determine total printing time, as can be appreciated from FIG. 3, the sheet feeding time cannot be reduced by itself. Therefore, the sheet feeding time is an obstruction tending to reduce a high speed printing operation.
The reason why printing is carried out twice is that the electric source lines are separated into a group of odd-number lines and a group of even-number lines. For instance, in order to cause the shaded part of the heat generating resistor unit in FIG. 8 to generate heat, the signal line 2 and the electric source lines 1 and 1' are selected. If, in this case, the line 2' is selected, the part indicated by the arrow also generates heat. That is, printing is achieved as required by selecting every other power source line with respect to a particular signal line.